Solid petrolatum or petroleum jelly, hereinafter referred to as petrolatum, has been widely used as a therapeutic agent for topical applications. This therapeutic agent possesses well known lubricating, softening and skin conditioning characteristics, and many dermatologists have endorsed the use of petrolatum as an effective hydrating agent and skin protectant for patients with dry or scaly skin.
Petrolatum consists of a mixture of hydrocarbons (including mineral oil and microcrystalline hydrocarbon waxes) of such nature that when the melted material is cooled to ordinary room temperatures, it congeals to a translucent, amorphous or jelly-like material.
The U.S. Pharmacopeia (U.S.P.) uses the terms white petrolatum and white petroleum jelly as being the same and describes them as a purified mixture of semi-solid hydrocarbons obtained from petroleum and wholly or nearly decolorized. Petrolatum is further defined as nearly having a melting point range of 38.degree. C. to 60.degree. C. or 100.4.degree. F. to 140.degree. F. and as having a consistency as determined by the U.S.P. official method of not less than 100 and not more than 275. A lesser decolorized grade is described in the National Formulary (N.F.) as a "yellow" grade and as free or nearly free from odor and taste.
Among the many attributes of petrolatum, which make its use in topical applications advantageous are its moisturizing efficacy, water barrier property, water repellency, resistance to being washed off by water, physiological inertness, and chemical inertness and stability.
The chief drawbacks of petrolatum in topical compositions are its greasiness, cosmetic inelegance and the inability to obtain a thin and consistent film over a large area of skin.
In the past, cosmetic compositions containing petrolatum have tried to avoid the drawbacks associated with petrolatum by keeping its concentration low, e.g. below 10% by weight of the total composition, or by adding additives to reduce the composition's greasy feel and appearance. Cosmetic compositions with low concentrations of petrolatum or with additives often do not exhibit all the therapeutic attributes of petrolatum. U.S. Pat. No. 3,852,475, issued Dec. 3, 1974, discloses a petrolatum-containing ointment which incorporates a hydrophobic starch in order to reduce the greasy feel and appearance of the ointment and its resistance to washing. However, the ointment of U.S. Pat. No. 3,852,475 still suffers from cosmetic inelegance and can not be easily spread into a thin film over a large area of skin.
The present invention overcomes the disadvantages associated with petrolatum in cosmetic compositions by providing a composition in the form of a foam. Additionally, the foam produced by the present invention has a substantially consistent foam density from initial dispensing to final dispensing, unlike the presently available cosmetic foams wherein the foam density increases dramatically as the container is emptied. Moreover, the foam of the present invention may be produced from a concentrate having a high petrolatum to emulsifier concentration ratio thereby maintaining the desirable skin-hydrating efficacy of petrolatum.
The present invention relates to a skin conditioning composition for application to the skin, said composition comprising an oil-in-water emulsion and a propellant packaged under pressure in an aerosol device or container under such conditions so as to form a foam having a foam density which changes less than 30 percent from intial dispensing to final dispensing from said aerosol device, said oil-in-water emulsion comprising
(a) at least 10 percent by weight of petrolatum, and generally about 10 to about 40 weight percent and preferably about 12.5 to about 35 weight percent,
(b) at least 50 weight percent water and generally about 50 to about 80 weight percent and preferably about 55 to about 77 weight percent, and
(c) an emulsifier having a hydrophile-lipophile balance value of 6 to 10 and generally present in an amount of about 2 to about 10 weight percent and preferably about 2 to about 5 weight percent,
said percentages being based on the total weight of said oil-in-water emulsion.